1. Field
The invention relates to a backlash-free planetary gear unit with a sun gear and with a ring gear which mesh with at least one first planet gear of a planetary stage wherein the first planetary stage comprises a first planet carrier on which the first planet gear is rotatably mounted, wherein there is furthermore at least one second planet gear in the planetary stage that also meshes with the ring gear and the sun gear.
2. Description of Related Art
In the field of high-precision planetary gear units, elimination of gear backlash between the gears transmitting the torque is considered an important objective. Therefore, planetary gear units are already know from prior art in which planet gears are divided and these planet gear halves are preloaded relative to each other.
Such a planetary gear unit is known, for example, from DE 10 2008 011 147 A1 In this gear unit, two planet gear halves are arranged on at least one planetary axis of rotation of a planet carrier and are preloaded relative to each other by a plurality of spring bars. This embodiment, however, requires forming separate recesses in the two planet gear halves for preloading in order to attach the spring bars to the planet gear halves. Firstly, this leads to weakening the planet gear geometry, and secondly, to a high production effort due to the machining the commonly high-strength steel gear. Moreover, under aspects of production technology, it is for reasons of space only possible to fabricate these recesses up to a certain planet gear diameter and therefore to a certain size of the planetary gear unit. For small models, it is technically no longer possible to attach such recesses